Britain has asked the United States to release five British residents from the military prison in Guantanamo Bay, Cuba, the Foreign Office said Tuesday.

Foreign Secretary David Miliband has written to Secretary of State Condoleezza Rice asking that the men be freed. The men are not British nationals, but had lived in the U.K. before they were detained.

Miliband has called for the release of Shaker Aamer, Jamil al-Banna, Omar Deghayes, Binyam Mohamed and Abdennour Sameur, the Foreign Office said in a statement.

"Discussions with the U.S. government about the release and return of these five men may take some time," the statement said. "They have decided to request the release and return of the five detainees who have links to the U.K. as former residents, having been granted refugee status, indefinite leave or exceptional leave to remain prior to their detention."

The Foreign Office said there may be security considerations when the men are returned to Britain. The government will "continue to take all necessary measures to maintain national security," the statement said.

Prime Minister Gordon Brown has hardened Britain's position over Guantanamo Bay, after ex-leader Tony Blair refused to press the U.S. to release the men.

In March, foreign office minister Kim Howells insisted Blair's government could not intervene in the cases of the former residents.